1. Field of the Invention
The present invention relates to a lower body structure for a vehicle, and more particularly to a lower body structure for a vehicle which limits collapsing of a side sill toward the interior of a vehicle compartment during a side collision.
2. Description of the Related Art
Conventionally, in vehicles such as automobiles, structures for suppressing the entry of a side sill into the interior of a vehicle compartment in an inclined manner during a side collision are known. For example, Japanese Utility Model Application Laid-Open (JP-U) No. 71980/1991 discloses a structure for suppressing the rotational displacement of a side sill by means of a scarf plate, and Japanese Utility Model Application Laid-Open (JP-U) No. 51687/1991 provides another example of such a structure. Hereafter, a description will be given of Japanese Utility Model Application Laid-Open (JP-U) No. 51687/1991.
As shown in FIG. 11, in this lower body structure for a vehicle, even if a large impact load is applied to a door or a center pillar 70 transversely from the outer side of the vehicle during a side collision, and a force is thereby produced for causing a side sill 72 to enter the interior of the vehicle compartment in an inclined manner, it is possible to prevent entry of the side sill 72 into the interior because the side sill 72 is supported by floor cross members 76 and 78 via a reinforcement 74 disposed on a vehicle transverse inner side surface 72A of the side sill 72.
With this lower body structure for a vehicle, an attempt is merely made to suppress entry of the side sill 72 in an inclined manner by supporting, in a load dispersing manner, the impact load from a side collision by the floor cross members 76 and 78 via the reinforcement 74. No attempt is made, however, to suppress the entry of the side sill in an inclined manner while also effectively absorbing the side collision impact load through the deformation of the vehicle body. Namely, two important considerations in design of the body structure which take the side collision into consideration are the following: First, the body structure must be able to suppress the entry of the center pillar into the interior of the vehicle compartment while preventing the inward collapsing of the side sill. Second, the body structure must be able to effectively absorb an impact load due to a side collision through the deformation of the vehicle body.
Contrary to these considerations with the lower body structure for a vehicle shown in FIG. 11, if the inward collapsing of the side sill 72 is suppressed by the floor cross members 76 and 78, the absorption of the impact load due to the side collision is primarily derived only from the impact absorbing capabilities based on the deformation of the center pillar 70. In this case, a large impact load is applied to a connecting portion between the center pillar 70 and the side sill 72, so that the center pillar 70 is bent at its connecting portion with the side sill 72, thereby making it impossible to produce a reaction force for resisting the impact load.
In addition, if it is assumed that the connection between the side sill 72 and the center pillar 70 is firm and is unbendable, the impact load at the time of the side collision is transmitted from the center pillar 70 to the floor cross members 76 and 78 via the side sill 72 (and the reinforcement 74), so that there is a possibility of the floor cross members 76 and 78 becoming bent substantially. If the floor cross members 76 and 78 are bent substantially, the side sill 72 collapses inwardly in conjunction with the bending of the floor cross members 76 and 78.